Skip to main content

This clever new technique could help us map the ocean floor — from the sky

Stanford University

A friend of mine who works in games design recently showed me a 3D model of the Earth, rendered in great detail using topographically accurate satellite data, so that we could soar through canyons and our respective neighborhoods at high speed like a pair of joyriding Supermen. “Let’s see if we can go underwater,” he said, exhilarated, as we flew out over the Pacific.

We couldn’t. The model, so stunningly accurate on land, apparently had zero data with which to model the undersea environment. It was an unrendered void beneath the water’s glassy surface, as if this was some subaquatic version of The Truman Show, and we had reached the end of the world.

Recommended Videos

Neither of us was particularly surprised. The shock would have been if the oceans had been rendered. Where would that information have come from? And how accurate would it have been? It would have meant the model’s creators knew something that even the world’s foremost oceanographers do not.

For all the justifiable excitement around exploring space in the 2020s (Elon Musk is “highly confident” that humans will be rocketing toward Mars by 2026), our planet’s oceans remain a largely uncharted and unknown domain that’s much closer to home. Water covers around 71 percent of Earth’s surface, with the freshwater stuff we drink accounting for a minuscule 3 percent, little more than a rounding error. But the overwhelming majority of the Earth’s oceans — up to 95 percent — are an unexplored mystery.

While we’re still a long way off from a Google Street View equivalent for the undersea world, a new project being carried out by researchers at Stanford University could pave the way for just such a thing in the future — and a whole lot more besides. Picture being able to fly an airplane over a stretch of water and see, with absolute clarity, what’s hiding beneath the waves.

It sounds impossible. As it turns out, it’s just really, really difficult.

The issue with lidar, the trouble with sonar

“Imaging underwater environments from an airborne system is a challenging task, but one that has many potential applications,” Aidan James Fitzpatrick, a graduate student in Stanford University’s department of and electrical engineering, told Digital Trends.

The obvious candidate for this imaging job is lidar. Lidar is the bounced laser technology most famous for helping (non-Tesla) autonomous vehicles to perceive the world around them. It works by emitting pulsed light waves and then measuring how long they take to bounce off objects and return to the sensor. Doing this allows the sensor to calculate how far the light pulse traveled and, as a result, to build up a picture of the world around it. While self-driving cars remain the best-known use of lidar, it can be used as a powerful mapping tool in other contexts as well. For example, researchers used it in 2016 to uncover a long-lost city hidden beneath dense foliage cover in the Cambodian jungle.

Lidar isn’t appropriate for this kind of mapping, though. Although advanced, high-power lidar systems perform well in extremely clear waters, much of the ocean — especially coastal water — tends to be murky and opaque to light. As a result, Fitzpatrick said, much of the underwater imaging performed to date has relied on in-water sonar systems that use sound waves able to propagate through murky waters with ease.

Unfortunately, there’s a catch here, too. In-water sonar systems are mounted to, or towed by, a slow-moving boat. Imaging from the air, using a flying airborne vehicle, would be more effective since it could cover a much greater area in less time. But it’s impossible since sound waves cannot pass from air into water and then back again without losing 99.9999 percent of their energy.

What comes to PASS

Consequently, while lidar and radar systems have mapped the entire Earth’s landscape (emphasis on the “land”), only around 5 percent of the global waters have been the subject of similar imaging and mapping. That’s the equivalent of a world map that only shows Australia, and leaves the rest of it dark like some unexplored Age of Empires map.

“Our goal is to propose a technology which can be mounted on a flying vehicle to provide large-scale coverage while using an imaging technique that is robust in murky water,” Fitzpatrick said. “To do this, we are developing what we have coined a Photoacoustic Airborne Sonar System. PASS exploits the benefits of light propagation in air and sound propagation in water to image underwater environments from an airborne system.”

Stanford University

PASS works like this: First, a special custom laser system fires a burst of infrared light that is absorbed by the first centimeter or so of water. Once laser absorption has occurred, the water thermally expands, creating sound waves that are able to travel into the water.

“These sound waves now act as an in-water sonar signal that was remotely generated using the laser,” Fitzpatrick continued. “The sound waves will reflect off underwater objects and travel back toward the water surface. Some of this sound – only about 0.06 percent – crosses the air-water interface and travels up toward the airborne system. High-sensitivity sound receivers, or transducers, capture these sound waves. The transducers [then] convert the sound energy to electrical signals which can be passed through image reconstruction algorithms to form a perceptible image.”

The things that lie beneath

So far, PASS is a work in progress. The team has demonstrated high-resolution, three-dimensional imaging in a controlled lab environment. But this, Fitzpatrick acknowledged, is in a “container the size of a large fish tank,” although the technology is now “close to the stage” where it could be deployed over a large swimming pool.

Stanford University

There is, of course, a slight difference between a large swimming pool and the entirety of Earth’s oceans, and this will require considerably more work. In particular, a big challenge to be solved before testing in larger, more uncontrolled environments is how to tackle imaging through water with turbulent surface waves. Fitzpatrick said that this is a head-scratcher, but it’s one that “surely has feasible solutions,” some of which the team is already working on.

“PASS could be used to map the depths of uncharted waters, survey biological environments, search for lost wreckages, and potentially much more,” he said. “Isn’t it strange,” he added, “that we have yet to explore the entirety of the Earth we live on? Maybe PASS can change this.”

Combining light and sound in order to solve the air-water interface would be a game changer. And after that? Bring on the army of mapping drones to finally help show us what lies beneath the ocean’s surface.

A paper describing the PASS project was recently published in the journal IEEE Access.

Luke Dormehl
I'm a UK-based tech writer covering Cool Tech at Digital Trends. I've also written for Fast Company, Wired, the Guardian…
The best portable power stations
EcoFlow DELTA 2 on table at campsite for quick charging.

Affordable and efficient portable power is a necessity these days, keeping our electronic devices operational while on the go. But there are literally dozens of options to choose from, making it abundantly difficult to decide which mobile charging solution is best for you. We've sorted through countless portable power options and came up with six of the best portable power stations to keep your smartphones, tablets, laptops, and other gadgets functioning while living off the grid.
The best overall: Jackery Explorer 1000

Jackery has been a mainstay in the portable power market for several years, and today, the company continues to set the standard. With three AC outlets, two USB-A, and two USB-C plugs, you'll have plenty of options for keeping your gadgets charged.

Read more
CES 2023: HD Hyundai’s Avikus is an A.I. for autonomous boat and marine navigation
Demonstration of NeuBoat level 2 autonomous navigation system at the Fort Lauderdale International Boat Show

This content was produced in partnership with HD Hyundai.
Autonomous vehicle navigation technology is certainly nothing new and has been in the works for the better part of a decade at this point. But one of the most common forms we see and hear about is the type used to control steering in road-based vehicles. That's not the only place where technology can make a huge difference. Autonomous driving systems can offer incredible benefits to boats and marine vehicles, too, which is precisely why HD Hyundai has unveiled its Avikus AI technology -- for marine and watercraft vehicles.

More recently, HD Hyundai participated in the Fort Lauderdale International Boat Show, to demo its NeuBoat level 2 autonomous navigation system for recreational boats. The name mashes together the words "neuron" and "boat" and is quite fitting since the Avikus' A.I. navigation tech is a core component of the solution, it will handle self-recognition, real-time decisions, and controls when on the water. Of course, there are a lot of things happening behind the scenes with HD Hyundai's autonomous navigation solution, which we'll dive into below -- HD Hyundai will also be introducing more about the tech at CES 2023.

Read more
This AI cloned my voice using just three minutes of audio
acapela group voice cloning ad

There's a scene in Mission Impossible 3 that you might recall. In it, our hero Ethan Hunt (Tom Cruise) tackles the movie's villain, holds him at gunpoint, and forces him to read a bizarre series of sentences aloud.

"The pleasure of Busby's company is what I most enjoy," he reluctantly reads. "He put a tack on Miss Yancy's chair, and she called him a horrible boy. At the end of the month, he was flinging two kittens across the width of the room ..."

Read more